1. Field of the Present Invention
The present invention relates to a radiation detector. In particular, the present invention relates to a radiation detector that includes plural pixels disposed in a matrix, that accumulates charges generated due to irradiation of radiation, and that detects the accumulated charge amount as information that represents an image.
2. Description of the Related Art
Recently, radiographic imaging devices (radiation image detection device) have been put into practice employing a radiation detector (radiation detection element) of a FPD (flat panel detector), or the like. Such radiation detector have an X-ray sensitive layer disposed on a TFT (Thin Film Transistor) active matrix substrate, and are able to directly convert X-ray information into digital data. Such FPDs have the merit that, in comparison to with previous imaging plates, images can be more immediately checked and video images can also be checked. Consequently the introduction of FPDs is proceeding rapidly.
Various types are proposed for such radiation detection elements. There are, for example, direct-conversion-type radiation detection elements that convert radiation directly to charge in a semiconductor layer, and accumulate the charge. There are also indirect-conversion-type radiation detection elements that first convert radiation into light with a scintillator, such as CsI:Tl, GOS (Gd2O2S:Tb) or the like, then convert the converted light into charge in a semiconductor layer and accumulate the charge.
A technology of using AEC sensors for detecting a total radiation irradiation amount to control a radiation source irradiating the radiation is known (for example, refer to Japanese Patent No. 4217506). In the technology described in Japanese Patent No. 4217506, AEC sensors (second radiation conversion elements) are formed in gaps between first radiation conversion elements (radiation detecting elements). In the technology described in Japanese Patent No. 4217506, the AEC sensors are formed on the same substrate as a substrate where the first radiation detection elements are formed.
According to the technology described in Japanese Patent No. 4217506, the AEC sensors are incorporated in the substrate where the first radiation detection elements, that are expensive components, are provided in a matrix. Therefore, when manufacturing defects occur in the AEC sensors or lines thereof, each substrate becomes a defective substrate. Namely, when manufacturing defects occur in the AEC sensors or lines thereof, each substrate needs to be discarded, even if manufacturing defects did not occur in the first radiation conversion elements provided in the matrix. Therefore, in the technology described in Japanese Patent No. 4217506, a manufacturing cost may be extraordinarily increased. When production of the substrate is finished, a shipping inspection is performed on the substrate where the AEC sensors are incorporated and the first radiation conversion elements are provided in the matrix. For this reason, a yield of the substrate may be represented by the following Expression.Yield=yield rate of first radiation conversion elements×yield rate of AEC sensors